Are Aliens Listening to Us?
To the best of our knowledge, we are alone in the universe.
However as a civilisation we have always wondered if life exists beyond the stars. What would they look like?, Would they come in peace? Do they even know of our existence?
The answer to this question largely depends on who they are and where they live. If this mysterious alien species can be found inhabiting a planet close to earth, have comparable intelligence and have the means of observing other planets there is a chance they may know we are here. If that isn’t the case, then it’s highly unlikely they know of our presence at all.
Thanks to the development of both radio and TV broadcasts in the last century, these signals may have travelled a distance of 116 light years, creating a sphere around earth where we may have an alien audience tuning in. If our neighbours are within a distance for our signals to reach their location, are technological advanced enough to receive our broadcasts, and have been able to carry out the relatively simple task of decoding our messages then there is a possibility that they know how we behave, what we look like and our culture and history.
Nearby Neighbours?
If we do have any neighbours in this 116 light year area around earth, they are more than likely to be situated on one of the rocky habitable planets orbiting a sun like star. With roughly 3000 to 5000 stars within this sphere about 2000 have sun like stars that are old enough to possess planets that could sustain life somewhat similar to our own. Unfortunately, this number decreases further as only 10% of these stars possess planets that reside in the habitable zone, resulting in between 100-500 planets within our broadcast bubble that could sustain life.
If we scale down this 116 light year sphere to the nearest 50 light years, we are able to see earth at the centre broadcasting to the local area. Since the initial broadcast of the XFiles in 1993, the signals have travelled 26 light years, allowing 6 habitable planets with potential audiences to tune in (Fig. 1). These planets cover a range of temperatures, masses and Earth Similarity indices. The earth similarity index, while not a measure of habitability is a scale from 0 to 1 to characterise how similar a planetary-mass object is to Earth. 0 being completely different to earth while 1 being exactly the same. This index is based on the planet’s radius, density, surface temperatures and escape velocity.
Aesthetics & Features
If we start to look a bit further out, you can see an additional 7 other confirmed habitable planets, which are capable of receiving our original Star Trek broadcasts released in 1966 (Fig. 2). Any galactic civilisations living on a habitable planet just shy of 90 light years away would be just picking up our very first TV broadcasts.
Beyond these relative limited distances, the odds of advances life, is purely a numbers game. There are several hundred billion stars in our galaxy, with only a inconceivably minuet fraction of them receiving our artificial signals is there any way that these distant civilisations could know anything about us?
Realistically, if they’re outside this noisy bubble we have created, all that they may know is that in the unfashionable end of the western spiral arm of the Galaxy lies a small unregarded yellow sun. Orbiting this at a distance of roughly ninety-two million miles is an utterly insignificant little blue green planet that has oxygen in its atmosphere. From this they could tell that there is ongoing photosynthesis here.
That may be of interest, but the likelihood of them sending a rocket to investigate earth just “because there’s grass here.” Is irreducibly small.